1. Field of the Invention
The present invention relates to an architectural material, and more particularly to an architectural material excelling in deodorizing, antimold, and antisoiling properties, and further to an architectural material excelling in peel resistance and durability, as well as a simple method for manufacturing an architectural material excelling in the deodorizing property and durability.
2. Description of the Related Art
As environmental problems have come more into focus, issues of deodorizing indoor spaces, and antimold and antisoiling properties of architectural material surfaces, and the like have come to attract attention.
Concerning deodorization, a method is conventionally known in which an apparatus or a piece of equipment is used for exhausting unwanted odors to the outside. As for antimold needs, the removal of molds by means of chemicals is performed by selecting an appropriate chemical according to the kind of mold. Regarding antisoiling needs, periodical cleaning by a person is only carried out.
Odors, molds, and soiling are essentially attributable to microorganisms, such as bacteria, yeasts and molds, and animal and plant cells. Accordingly, the attempt to deodorize and prevent molds and fouling can, in principle, be considered as the destruction of these cells, i.e., sterilization. Generally known methods of sterilization include heating, irradiation with ultraviolet or other radioactive rays, cell destruction by means of ultrasonic waves, electric sterilization, gas sterilization, and sterilization using chemicals including antibiotics. In addition, a sterilization method using fine particles of a photo-semiconductor is also known. As part of this line of effort, basic research is being undertaken on the removal of organic and inorganic contaminants in water and air by using titanium dioxide photocatalysts. Namely, semiconductors such as titanium dioxide are known to exhibit a photocatalytic function by means of a light of a specific wavelength and possess deodorizing and antimold functions through their powerful oxidizing action. It is stated on page 211 of Vol. 13, No. 5 (1985), of the "Bohkinbohkabi (Fungus and Mold Prevention) Journal" that a fixed film consisting of fine particles of titanium dioxide is useful as a sterilizing reactor. In addition, Japanese Patent Publication No. 9850/1990 discloses a method of purifying wastes by the use of a semiconductor, such as titanium oxide, which carries a metal or a metal oxide therein.
Conventionally, titanium dioxide, iron oxide, tungsten oxide, silicon oxide and the like having a semiconductor function, or such metals carrying a second metal, such as platinum, thereon for the purpose of improving the catalytic function are used as photocatalysts. To make use of the deodorizing and antimold functions, such metals are pulverized into fine particles to form a fixed film on a surface, or the fine particles are used by being dispersed in an object to be treated.
Although various studies have been made regarding methods of imparting the deodorizing and antimold functions to architectural materials by making use of the photocatalytic function, in accordance with the above-described method, particles are troublesome to handle as materials. The known fixed films have only been used experimentally, and their strength is not sufficient. The fabrication of semiconductor materials into thin film has been industrially difficult, and has not yet been put to practical use.
As described above, for deodorizing, an apparatus or piece of equipment must have a sophisticated function and made large in size, which results in high running cost and is clearly uneconomical. Moreover, since air is exhausted through an opening of a limited size, it is extremely difficult to deodorize the entire indoor space. The conventional antimold method is no more than a short-term measure, and the long-term maintenance of the antimold property remains unresolved. As for the antisoiling property, if the cleaning of the outer wall surfaces of large buildings is considered, huge expenses are required for manpower needed for cleaning, and, since the long-term maintenance of the antisoiling property is not ensured, repeated cleaning operations are unavoidably carried out. Furthermore, as for the deodorization, antimolding, and antisoiling of architectural materials, the conventional sterilization methods are either impractical or difficult to put to practical use in the light of long-term maintenance, economy, technical difficulties, inexperience in techniques, and the like.